M3 Class 2 Molybdenum High Speed Tool Steel (UNS T11323)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Fabrication and Heat Treatment
     Hardening
     Machinability
     Tempering
Applications

Introduction

High-speed tool steels are divided into molybdenum high-speed steels and tungsten high-speed steels. Group M steels or molybdenum high-speed steels have less initial cost. Tungsten is found in types M1 to M10, except type M6, and cobalt is not present in these types of molybdenum high-speed steels.

M3 Class 2 molybdenum high speed tool steel, also known as tungsten moly high speed tool steel, provides excellent wear resistance in severe cutting operations.

Chemical Composition

The chemical composition of M3 Class 2 molybdenum high speed tool steel is outlined in the following table:

Element Content (%)
Fe
Balance
C 1.15-1.25
Mn 0.15-0.40
Si 0.20-0.45
Cr 3.75-4.50
Ni 0.3
Mo 4.75-6.50
W 5.00-6.75
V 2.75-3.75
Cu 0.25
P 0.03
S 0.03

Physical Properties

The following table shows the physical properties of M3 Class 2 molybdenum high speed tool steel.

Physical properties Metric Imperial
Density 8.16g/cm3 0.294 lb/in3

Mechanical Properties

The mechanical properties of M3 Class 2 tool steel are displayed in the following table.

Mechanical properties Metric Imperial
Hardness, Rockwell C (tempered at 1150°F) 57.0 - 59.0 57.0 - 59.0
Hardness, Rockwell C (as quenched) 65.0 - 66.0 65.0 - 66.0
Izod impact unnotched 32.5 - 42.0 J 24.0 - 31.0 ft-lb
Poisson's ratio 0.27-0.30 0.27-0.30
Elastic modulus 190-210 GPa 27557-30458 ksi

Other Designations

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Equivalent materials to M3 Class 2 molybdenum high speed tool steel are:

  • ASTM A600 (M-3, Cl.2)
  • DIN 1.3342
  • DIN 1.3344
  • SAE J437 (M3)
  • SAE J438 (m3)
  • UNS T11323

Fabrication and Heat Treatment

Hardening

M3 Class 2 molybdenum high speed tool steel is hardened when preheated to 871°C (1599°F) and it is then soaked thoroughly, furnace cooled through 593°C (1099°F) and finally air cooled.

Machinability

In the annealed condition, M3 Class 2 tool steel is referred to as “medium” machinability tool steel. It has a machinability rating of 50% when compared to Group W steels. It has very poor grinding capability even though it can be shaped by a grinding process.

Tempering

Triple tempering is recommended for M3 Class 2 steel. Specified tempering temperatures enable obtaining many different hardness values and this steel is usually tempered at 566°C (1051°F).

Applications

M3 Class 2 molybdenum high speed tool steels are used in the production of taps, broaches, end mills, milling cutters and reamers.

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